Kruppel-like factors (KLFs) are transcription factors that regulate developmental programs. In mice without KLF2, embryonic expression of gamma-y- and beta-H-1 globin mRNA is significantly reduced. The goal is to identify novel genes involved in primitive erythropoiesis and those regulated by KLF2. The first specific aim is to generate an expression profile of mouse primitive erythropoiesis. This involves isolating erythroid and epithelial cells by laser capture microdissection from E9.5 yolk sacs. RNA from both cell types will be hybridized to Affymetrix GeneChip(R) 430A 2.0 arrays for microarray analyses. Supervised learning methods will be utilized to identify erythroid-specific genes. In specific aim 2, differentially expressed genes will be identified in wild-type and KLF2-/- erythroid cells with the LCM/microarray strategy. Hierarchical clustering and supervised learning methods will be employed to identify differences in gene expression due to the loss of KLF2. For specific aim 3, differential expression of erythroid genes between wild-type and KLF2-/- embryos will be verified with quantitative RT-PCR. This work will provide novel approaches to treat individuals with beta-thalassemia and sickle cell anemia.